The present invention relates generally to switching devices, and more particularly to an electromagnetic relay of the heavy duty type.
Recent advances in integrated circuit techniques have promoted efforts in developing compact, light-weight devices for use in communication equipments, control systems and household appliances. In automotive vehicles for example, the recent tendency is toward using integrated circuits to control a variety of peripheral devices that require a heavy current for operation. Although semiconductor switching devices may be considered as an interface between the integrated circuits and peripheral devices in order to take advantage of their compactness and their adaptability to integrated circuits during manufacture, they are inappropriate due to their incapability to operate under heavy current loads and particularly due to their susceptability to surge currents caused by lightning or the like. Electromagnetic relays can be considered as best devices to act as such interfaces, although they occupy a substantial volume.
A small-sized electromagnetic relay of the heavy duty type which is known in the art for use in printed circuits comprises a pair of stationary contact members. Each of these contact members is a rectangular metal strip which is bent into a generally L-shaped configuration so that their contact elements are located in opposite positions when secured to insulative supports between which a core-and-armature structure is located, with a movable contact being located between the stationary contacts. Disadvantages are that the contact spacing is not precisely determinable and that the prior art configuration does not permit the use of an automatic assemblage machine with which the stationary contact members are secured to the supports in a single operation.
In a switching device shown and described in U.S. Pat. No. 4,044,212, two stationary contact members are punched from a single metal strip into a shape contoured so that they are snap-action engaged with insulative supports. While this switching device may be successful in eliminating the problems mentioned above, there is still a disadvantage in that heat generated by arcing between contacts tends to be conducted to one of the insulative supports to fuse a portion of it, causing the contact spacing to deviate from the set value, or vaporize it, generating organic gas which would contaminate the contact elements and reduce the insulation resistance.